Diagnosis and TNM

How is prostate cancer diagnosed?

When faced with the suspicion of prostate cancer, (usually upon detecting a raised PSA or urinary problem) the physician proceeds to a rectal examination. This procedure allows the experienced specialist to identify any irregularity or hardened area in the prostate which might be due to cancer.

In order to avoid causing unnecessary discomfort during the digital rectal examination (DRE), the doctor inserts a gloved and lubricated finger into the anus for a pain free palpation.

If the suspicion is confirmed, it is necessary to proceed to a biopsy, a procedure which is in theory indicated for men presenting a PSA greater than 4 ng/ml or presenting prostatic irregularities. The biopsy and subsequent analysis of the extracted tissue allows to either confirm or rule out the presence of prostate cancer.

In order to carry out the biopsy, a sample type needle is introduced via the rectum under the guidance of a trans-rectal ultrasound that enables the accurate localisation of the area or areas to be sampled.

Prior to carrying out the trans-rectal ultrasound, it is necessary to position an echographic probe inside the rectum, a process which causes some discomfort, as does the subsequent presence of the probe. Still, the patient undergoing the examination must remember at all times that this examination is necessary to his wellbeing and that despite the discomfort experienced, nothing serious can happen.

It is nevertheless perfectly bearable, especially if one take into account that the duration of the procedure from the positioning of the  echographic probe to the completion of the biopsy amounts to a total of 10 to 20 minutes. It is worth bearing in mind that the biopsy itself is very quick.

The sample needle enables the extraction of a cylinder of prostate tissue. In the event that there is/are no suspicious area/s towards which to aim the needle, the common procedure is to carry out a minimum of 6 punctures, up to maximum of 14 or 15, in order to cover the full expanse of the prostate.

The extracted samples are then submitted to the pathologist in order to establish the diagnosis, and in the event that this diagnosis is indeed cancer, the Gleason grade (for further information, please refer to the “Cancer of the prostate” section).

Does the diagnosis involve any other tests?

Once the diagnosis of prostate cancer has been established, a series of complementary tests are carried out that are aimed at assessing the patients general health and establishing whether or not the disease has spread beyond the prostate.

It is therefore necessary to order blood tests (full haemogram and platelets) and a biochemical blood analysis (testing levels of alkaline phosphatase, transaminase, gamma GT, bilirubin, urea, creatinine, cholesterol and glycaemia). These are an indicator of the patient’s general state of health and the potential presence of bone metastases.

In order to provide an objective answer with regard to whether or not the pelvic lymphnodes are affected, and to rule out metastases in the liver, an abdominal CAT scan is ordered. If preferred, MRI (magnetic resonance imaging)  is a likely alternative.

Bone gammagraphy is a further test which is of major importance. This is carried out by means of the intravenous administration of radioactive material which characteristically attaches to bone tissue, thus providing a “map” of the skeleton. Differences in the uptake of the radioactive material allow the detection of potential metastases in the bones. The radioactive isotopes tend to stick better to metastases that normal bone tissue.

It must be noted that the radioactive material used emits very short waves and has a very short half-life.

The first characteristic, that is, the short waves, ensures that the examination, even though it makes use of radioactive material, presents no danger to those who find themselves in close proximity to the patient (friends and relatives).

The second, that is, the short half-life, means that the radioactivity dies out after just a few hours, making it very safe.

At that particular point in time, what are the conclusions that can be drawn from a medical point of view ?

We are able to establish the so-called spread diagnosis, meaning that we already know the amount of cancer in a particular prostate cancer patient, that is, the extent of tumour spread within the prostate, to surrounding tissue, the lymphnodes and other organs. The spread diagnosis is the most important and simplest prognostic marker. Its role is essential in determining the choice of treatment.

Are the spread diagnosis, stage and TNM equivalent  ?

Yes, although stages and TNM are classification are used by physicians as much to express the spread diagnosis in each patient as to facilitate communication between healthcare professionals.

The TNM system was devised in 1944 by a French physician, Doctor Pierre Denoix. It was very well received and its use consequently became widespread across the world.

The system is based on patient survival rates in each TNM situation and is used in order to draw up a suitable treatment plan and establish the prognosis.

For prostate cancer, only the TNM classification is used whilst the stages system is not. The stages (there tend to be 4) provide a summary of the various TNM states, but TNM is deemed more useful with regard to prostate cancer in particular.  .

Is there only one modality with the TNM?

There are two types of TNM, the clinical kind (established according to the aforementioned tests and the medical examination)  and the pathological kind, or pTNM.

In addition, pTNM also complements all the microscopic findings obtained by the pathologist upon examining the extracted tissue.

What are the potential TNM scenarios with regard to prostate cancer?

These are as follows:

T1: The tumour is neither detectable nor palpable during digital rectal examination, but cancerous cells are found, either by transurethral section of the prostate, in the biopsy or prostatectomy.

T1 are subdivided into the following:

T1a: This is a T1 where microscopical examination shows  that only 5% of the extracted tissue contains cancerous cells, whilst the remaining 95% is benign. PSA is normal.

T1b: T1 with over 5% of cancerous tissue. Normal PSA.

T1c: Either of the above, but with a PSA that suggests the presence of carcinoma.

T2: A tumour is detected in the prostate by means of rectal palpation, but only within the gland, that is, there is no spread to surrounding tissue or structures.

T2 is subdivided into the following:

T2a: The tumour is localised in either the left side or the right side of the prostate.

T2b: The tumour affects both sides, left and right.
T3: The tumour has spread beyond the prostate capsule.

T3 is subdivided into:

T3a: Unilateral or bilateral extracapsular spread, excluding other tissues and organs.

T3b: The seminal vesicles are affected but no other organs.
T4: The tumour is either  fixed (i.e., stuck to external structures) or invasive.

T4 is subdivided into:

T4a: The tumour invades the neck of the urinary bladder, the external sphincter or the rectum.

T4b: The tumour either invades the elevator muscles or is fixed to the lateral wall of the urinary bladder.

How is the degree to which lymph nodes are affected classified?

There are three possible scenarios:
NX: The lymphnodes cannot be assessed.
N0: The cancer does not affect the lymphnodes.
N1: One or more local lymphnodes are affected.

What about metastases?

As with lymphnodes:

MX:Remote metastases can not be assessed
M0:The cancer has not spread beyond the local lymphnodes.

M1: the disease has spread to lymphnodes beyond those of the pelvic area and/or to bones, liver, lungs, brain, etc.


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